Distributed protection switching architecture for point-to-point microwave radio systems

ABSTRACT

A system and method for protecting a received data stream. Active receivers and standby receivers are provided, each adaptable to receive a data stream on a traffic channel. Plural data processing units are operatively in communication with the receivers. At least one of the plural DPUs provides a switching signal to the receivers to switch the state of the active receiver to standby and the state of the standby receiver to active as a function of a quality measurement of the received data stream via the traffic channel.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S.Nonprovisional patent application Ser. No. 12/861,779 filed Aug. 23,2010, and entitled “Distributed Protection Switching Architecture forPoint-to-Point Microwave Radio Systems,” which in turn is a continuationof U.S. Nonprovisional patent application Ser. No. 11/655,837 filed Jan.22, 2007, and entitled “Distributed Protection Switching Architecturefor Point-to-Point Microwave Radio Systems.” Both U.S. Nonprovisionalpatent application Ser. No. 12/861,779 and U.S. Nonprovisional patentapplication Ser. No. 11/655,837 are hereby incorporated herein byreference.

BACKGROUND

Protection switching is an essential feature in microwave and millimeterwave radio systems to meet system reliability objectives. There existmany different methods and systems to achieve an increase in systemreliability and availability of protection switching. For example, atypical protection switching architecture may be realized as redundantsets of modules that are subparts of a higher level component andimplement functions of the component. The component may be structuredand controlled such that there are redundant modules for each feature orgroup of features of importance. In such an architecture there generallyare at least two modules which implement each important function. Thesemodules are typically referred to as redundant modules or redundantmodule sets. Prior art protection switching is generally constructed ofone or more sets of these redundant modules, the premise being if acurrently selected set fails, one other unselected set may be promptlysubstituted for the failed set and the component can resume providingcommunication or the relevant function.

A methodology and mechanism is required to control and communicateinformation regarding control of which of the redundant sets is theactive or standby set. When this function is structured to operatewithout intervention of separate equipment or entities, it is commonlyreferred as automatic protection switching. In prior art radio systems,these switching decisions are generally made by a central controller.For example, prior art radio systems typically utilize a single centralcontroller responsible for the control of protection switches based uponcomponent and path alarms collected from various modules in a system. Asa result, when the controller fails, no further switch decisions may bemade, and the corresponding protection switch is frozen at its laststate. Thus, any further component, equipment or path failures mayresult in a traffic or communication outage. Further, prior artmechanisms utilized to communicate with the central controller and anyqueuing associated therewith add delay in the reconfiguration of thecomponent or equipment. Therefore, it is desirable to realize protectionswitching as a distributed solution so that communication may beprotected from single failures.

Typical prior art automatic protection systems for network elements havealso generally comprised, for example, redundant facility equipmentwherein a detected failure in one of the redundant sides results in aswitch from one redundant side to the other. In such an architecture, anentire line of protection equipment is substituted for another even if afailure occurred in only one place in the working channel. Such anapproach is inflexible since it fails to maximize available equipment.Moreover, switching decisions are typically be made by the systemcontroller and all information relevant to the protection switchingdecision must still be sent to the system controller. Since the systemcontroller services all information in this type of architecture, asignificant amount of time is required to accomplish the switchover, andall the elements on the data path are still required to be switchedduring a switching event.

It is apparent that the aforementioned processes are inefficient andfail to provide the necessary redundant protection switching required inmicrowave and millimeter wave radio systems. Accordingly, there is aneed for a novel method and system that would overcome the deficienciesof the prior art. A further need exists for distributed protectionswitching in a microwave and millimeter wave radio systems. Thus,embodiments of the present subject matter may employ distributedprotection switching architecture providing individual controllers onplural intelligent modules involved in a protection redundant path.Embodiments of the present subject matter may also provide distributedalarm collection and switch decision making as well as switch executionamong the intelligent modules. Additional embodiments of the presentsubject matter may also provide an exchange of information betweenmodules through an in-band communication protocol. Embodiments of thepresent subject matter thus eliminate single failure points that couldrender a protection switch inoperative, and thus improve a radiocommunication system's reliability.

An embodiment of the present subject matter provides a method forprotecting a received data stream. The method comprises the steps ofproviding an active receiver and a standby receiver, each adaptable toreceive a data stream and providing a plurality of data processing units(DPUs) operatively in communication with the active receiver and thestandby receiver. The method further comprises measuring the quality ofthe data stream by the receivers, providing a signal to the plural DPUsas a function of a quality measurement of the received data stream, andprocessing the signal at ones of the plural DPUs. A switching may thenbe provided from at least one of the plural DPUs to switch the state ofthe active receiver to standby and the state of the standby receiver toactive in response to the switching signal.

Another embodiment of the present subject matter provides a method forprotecting a received data stream. The method comprises the steps ofproviding an active receiver and a standby receiver, each adaptable toreceive a data stream on a traffic channel and providing a plurality ofDPUs operatively in communication with the active and standby receivers.The method further comprises providing a switching signal from at leastone of the plural DPUs to switch the state of the active receiver tostandby and the state of the standby receiver to active as a function ofa quality measurement of the received data stream via the trafficchannel.

A further embodiment of the present subject matter provides a system forprotecting a received data stream comprising a plurality of apredetermined number of active receivers, a plurality of a predeterminednumber of standby receivers, and a plurality of a predetermined numberof DPUs. At least one of the plural active receivers and at least one ofthe plural standby receivers further comprise a switching controlleradaptable to provide a signal as a function of a quality measurement ofa received data stream, the controller adaptable to change the state ofits respective receiver from standby to active or vice-versa. The DPUsfurther comprise a switching unit operatively in communication with theswitching controllers, capable of receiving the signal, capable ofproviding a switching signal to at least one switching controller tochange the state of the respective receiver.

An additional embodiment of the present subject matter provides a methodfor communicating between redundant controllers and plural microwavemodules. The method comprises the steps of providing an active moduleand a standby module, each adaptable to transmit or receive a datastream and measure the quality of the data stream. The method furthercomprises providing a plurality of DPUs operatively in communicationwith the active module and the standby module, and communicating signalsto ones of the plural DPUs from the active and standby modules as afunction of a quality measurement of the received data stream via achannel carrying the data stream. The state of the active module maythen be switched to standby and the state of the standby module toactive in response to a switching signal provided from one of the pluralDPUs via the channel.

These embodiments and many other objects and advantages thereof will bereadily apparent to one skilled in the art to which the inventionpertains from a perusal of the claims, the appended drawings, and thefollowing detailed description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a distributed protection system according to an embodiment ofthe present subject matter.

FIG. 2 is a flowchart illustrating a method for protecting a receiveddata stream according to an embodiment of the present subject matter.

FIG. 3 is a flowchart illustrating another method for protecting areceived data stream according to an embodiment of the present subjectmatter.

FIG. 4 is a flowchart illustrating a method for communicating betweenredundant controllers and plural microwave modules according to anembodiment of the present subject matter.

DETAILED DESCRIPTION

With reference to the figures where like elements have been given likenumerical designations to facilitate an understanding of the presentsubject matter, the various embodiments of a method and system fordistributed protection switching in a radio system are herein described.

FIG. 1 is a distributed protection system according to an embodiment ofthe present subject matter. With reference to FIG. 1, a system 100 isprovided comprising an active receiver 10 and a standby receiver 20. Theactive receiver 10 may include a switching controller 12 adaptable toprovide a signal 14 as a function of a quality measurement of a receiveddata stream 2. Similarly, the standby receiver 20 may also include aswitching controller 22 adaptable to provide a signal 24 as a functionof a quality measurement of the received data stream 2. The signals 14,24 may be utilized to change the state of the active receiver 10 fromactive to standby and the state of the standby receiver 20 from standbyto active. The quality measurement may be a function of the signalstrength, signal to noise ratio, bit error rate, and/or received powerlevel of the received data stream 2. While one active receiver 10 andone standby receiver 20 are shown, such an illustration is not intendedto limit the scope of the claims appended herewith. For example, thenumber of active receivers 10 may be greater than, less than, or equalto the number of standby receivers 20. Further, while the instantembodiment is presently discussed with reference to receivers, thepresent subject matter is equally applicable to transmitters.Embodiments of the present subject matter may also be modularized, thatis, the receivers may be receiver modules and the transmitters may betransmitter modules.

The system further comprises plural data processing units (DPUs) 30, 35comprising a switching unit 40 and switching controllers 32, 37, theDPUs 30, 35 operatively in communication with the switching controllers12, 22. Additional or fewer DPUs may be provided in the system asnecessary. The DPUs may generally communicate with the switchingcontrollers 12, 22 via an in-band communication protocol. The in-bandcommunication protocol may be based upon the concept of shared registerwith interrupt notification of change of state. This communication maybe employed between the DPUs 30, 35 or DPU modules and each of thereceivers or modules involved in the protection switching. For example,a total of 64 bit registers may be implemented for each point-to-pointlink between two modules. The information provided may be processed as asingle entity and a flag bit utilized at each end of the link to preventpartial transmission of information during updates. Thus, the in-bandcommunication may link modules directly involved in the protectionswitching, to eliminate unnecessary dependence on other modules such asa system controller. Furthermore, since the communication is in-band, aslong as data traffic is passing though, the information required forprotection switching is available to make a switch decision.

The controllers may collect data, alarms and/or threshold informationand provide such to the DPUs 30, 35 where the data, etc. is processedand a switching decision made and provided to the switching unit 40. Theswitching controllers 12, 22 may be in communication with the DPUs 30,35 via a network line such as a SONET line, OC-12 line, OC-24 line,OC-48 line or other optical carrier line. The switching unit 40 may be a1+1 receiver hitless switch, 1+1 monitored hot standby switch, lineinterface unit 1+1 switch, data processing unit 1+1 switch, or otherswitching means utilized in the art. The switching unit 40 is capable ofreceiving signals 14, 24 and providing a switching signal 4 to at leastone of the controllers to change the state of the respective activereceiver 10 and/or standby receiver 20. The switching signal 4 may beprovided to the respective receivers 10, 20 via a channel carrying thedata stream 2. Further, the switching signal may be a synchronoustransport signal, e.g., STS-1, etc.

Thus, switching decisions may be distributed among receivers and/ormodules, dependent upon the type of protection switching schemeemployed. For example, in system employing a 1+1 receiver switch, theDPUs 30, 35 process receiver alarms, make the switching decision andexecute the decision. Therefore, due to the redundancy of the DPUs 30,35, the prior art problem of inoperative protection switching due tocontroller failure may be eliminated. Further by example, in a prior art1+1 redundant system, system unavailability may be provided by thefollowing relationship:U=U _(S) +U _(B) ² +U _(B) *U _(PSW)  (1)

U_(S) represents the series path unavailability, U_(B) the parallel pathunavailability, and U_(PSW) the unavailability of protection controlcircuitry. Systems and methods employing embodiments of the presentsubject matter provide system unavailability according to the followingrelationship:U=U _(S) +U _(B) ² +U _(B)*(U _(PSW))²  (2)

Thus, the third term in the second equation, U_(B)*(U_(PSW))², is of athird order and becomes negligible when compared to the second term,U_(B) ². Therefore, due to the distributed redundant controllerarchitecture of the present subject matter coupled with redundantin-band protection switching signaling links, the overall reliability ofthe protection switch feature and consequently system reliability may begreatly enhanced.

FIG. 2 is a flowchart illustrating a method for protecting a receiveddata stream according to an embodiment of the present subject matter.With reference to FIG. 2, in step 202, an active receiver and a standbyreceiver are provided. Each of the receivers are adaptable to receive adata stream. In step 204, plural DPUs are provided operatively incommunication with the active and standby receivers. The quality of thedata stream may be measured by the active and standby receivers in step206. A signal may then be provided to the plural DPUs as a function of aquality measurement of the received data stream in step 208. The qualitymeasurement may be a signal strength, signal to noise ratio, bit errorrate, and/or received power level of the received data stream.

In an alternative embodiment, this signal may comprise communicating byshared register with an interrupt notification of change of state.Further, the interrupt notification may be provided as a function of aflag bit at the end of a portion of the data stream. The signal isprocessed at ones of the plural DPUs in step 210, and a switching signalis provided from at least one of the plural DPUs in step 212. Theswitching signal may be utilized to switch the state of the activereceiver to standby and the state of the standby receiver to active. Inan additional embodiment of the present subject matter, the switchingsignal may be provided via a channel carrying the data stream.

FIG. 3 is a flowchart illustrating another method for protecting areceived data stream according to an embodiment of the present subjectmatter. With reference to FIG. 3, in step 302, an active receiver and astandby receiver are provided. Each of the receivers are adaptable toreceive a data stream on a traffic channel. In step 304, a plurality ofDPUs may be provided operatively in communication with the active andstandby receivers. A switching signal may then be provided from at leastone of the plural DPUs in step 306. The switching signal may be utilizedto switch the state of the active receiver to standby and the state ofthe standby receiver to active as a function of a quality measurement ofthe received data stream via the traffic channel. Of course, the qualitymeasurement may be a signal strength, signal to noise ratio, bit errorrate, and/or received power level of the received data stream. Analternative embodiment of the present subject matter may further measurethe quality of the data stream by the receivers, provide a signal to theDPUs as a function of the quality measurement, and process the signal atones of the plural DPUs. The signal provided to the plural DPUs may bebased upon the concept of shared register with an interrupt notificationof change of state. Further, the interrupt notification may be providedas a function of a flag bit at the end of a portion of the data stream.

FIG. 4 is a flowchart illustrating a method for communicating betweenredundant controllers and plural microwave modules according to anotherembodiment of the present subject matter. With reference to FIG. 4, instep 402, an active module and a standby module are provided. Each ofthe modules are adaptable to transmit or receive a data stream andmeasure the quality of the data stream. The modules may be receiver ortransmitter modules. Plural DPUs are provided in step 404. Each of theplural DPUs are operatively in communication with the active and standbymodules. In step 406, signals are communicated to ones of the pluralDPUs from the active and standby modules. Any number of DPUs may beprovided, e.g., 1, 2, 3, 4, etc. The signals may be communicated as afunction of a quality measurement of the received data stream via achannel carrying the data stream. The signals communicated to the pluralDPUs may be based upon the concept of shared register with an interruptnotification of change of state. Further, the interrupt notification maybe provided as a function of a flag bit at the end of a portion of thedata stream. Of course, the quality measurement may be a signalstrength, signal to noise ratio, bit error rate, and/or received powerlevel of the received data stream. In step 408, the state of the activemodule may be switched to standby and the state of the standby modulemay be switched to active in response to a switching signal providedfrom any one of the plural DPUs via the traffic channel. In analternative embodiment of the present subject matter, any one but notall of the DPUs may provide the switching signal.

It is thus an aspect of embodiments of the present subject matter toresolve single point failure problems in single or system controllers ofconventional protection switching architectures.

As shown by the various configurations and embodiments illustrated inFIGS. 1-4, a method and system for distributed protection switching in amicrowave or millimeter wave radio system have been described.

While preferred embodiments of the present subject matter have beendescribed, it is to be understood that the embodiments described areillustrative only and that the scope of the invention is to be definedsolely by the appended claims when accorded a full range of equivalence,many variations and modifications naturally occurring to those of skillin the art from a perusal hereof.

What we claim is:
 1. A method, comprising: receiving a data stream by afirst receiver having an active state and a standby state, the firstreceiver being in the active state; receiving the data stream by asecond receiver, the second receiver having an active state and astandby state, the second receiver being in the standby state; measuringby the first receiver a characteristic of the data stream to generate afirst quality measurement; measuring by the second receiver thecharacteristic of the data stream to generate a second qualitymeasurement; providing a quality signal to one or more data processingunits (DPUs), the quality signal being a function of the first qualitymeasurement and the second quality measurement; and generating by theone or more DPUs a switching signal configured to switch the firstreceiver from the active state to the standby state and to switch thesecond receiver from the standby state to the active state, theswitching signal being based on the quality signal.
 2. The method ofclaim 1, wherein the first receiver includes a switching controller andthe second receiver includes a switching controller.
 3. The method ofclaim 2, wherein measuring by the first receiver the characteristic ofthe data stream is performed by the switching controller of the firstreceiver, and measuring by the second receiver the characteristic of thedata stream is performed by the switching controller of the secondreceiver.
 4. The method of claim 1, further comprising a first set ofone or more receivers having an active state and a standby state, theone or more receivers of the first set being in the active state, and asecond set of one or more receivers having an active state and a standbystate, the one or more receivers of the second set being in the standbystate.
 5. The method of claim 4, wherein the number of the one or morereceivers of the first set is greater than, less than, or equal to thenumber of the one or more receivers of the second set.
 6. The method ofclaim 1, further comprising providing from the one or more DPUs theswitching signal via a channel carrying the data stream.
 7. The methodof claim 1, wherein providing the quality signal to the one or more DPUsfurther comprises communicating by shared register with an interruptnotification of change of state.
 8. The method of claim 7, wherein theinterrupt notification is provided as a function of a flag bit in thedata stream.
 9. The method of claim 1, wherein measuring by the firstreceiver the characteristic of the data stream and measuring by thesecond receiver the characteristic of the data stream includesmeasuring: a signal strength of the data stream, a signal to noise ratioof the data stream, a bit error rate of the data stream, a receivedpower level of the data stream, or a combination thereof.
 10. A system,comprising: a first set of one or more receivers for receiving a datastream, the one or more receivers of the first set measuring acharacteristic of the data stream to generate a first qualitymeasurement, the one or more receivers of the first set having an activestate and a standby state, being in the active state, and beingswitchable from the active state to the standby state by a switchingsignal; a second set of one or more receivers for receiving the datastream, the one or more receivers of the second set measuring thecharacteristic of the data stream to generate a second qualitymeasurement, the one or more receivers of the second set having anactive state and a standby state, being in the standby state, and beingswitchable from the standby state to the active state by the switchingsignal; and one or more data processing units (DPUs) configured toreceive a quality signal, the quality signal being a function of thefirst quality measurement and the second quality measurement, the one ormore DPUs configured to generate the switching signal based on thequality signal.
 11. The system of claim 10, further comprising aswitching unit, the switching unit capable of providing the switchingsignal to the one or more receivers of the first set and the one or morereceivers of the second set.
 12. The system of claim 11, wherein theswitching unit includes one or more of: 1+1 receiver hitless switch, 1+1monitored hot standby switch, line interface unit 1+1 switch, and dataprocessing unit 1+1 switch.
 13. The system of claim 10, wherein thenumber of the one or more receivers of the first set is greater than,less than, or equal to the number of the one or more receivers of thesecond set.
 14. The system of claim 10, wherein the measuredcharacteristic includes: a signal strength, a signal to noise ratio, abit error rate, a received power level, or a combination thereof. 15.The system of claim 10, wherein the switching signal is provided via achannel carrying the data stream.
 16. The system of claim 10, whereinthe one or more DPUs are further configured to receive the qualitysignal via a shared register with an interrupt notification of change ofstate.
 17. The system of claim 16, wherein the interrupt notification isprovided as a function of a flag bit in the data stream.
 18. A method,comprising: means for receiving a data stream by a first receiver havingan active state and a standby state, the first receiver being in theactive state; means for receiving the data stream by a second receiver,the second receiver having an active state and a standby state, thesecond receiver being in the standby state; means for measuring by thefirst receiver a characteristic of the data stream to generate a firstquality measurement; means for measuring by the second receiver thecharacteristic of the data stream to generate a second qualitymeasurement; means for providing a quality signal to one or more dataprocessing units (DPUs), the quality signal being a function of thefirst quality measurement and the second quality measurement; and meansfor generating by the one or more DPUs a switching signal configured toswitch the first receiver from the active state to the standby state andto switch the second receiver from the standby state to the activestate, the switching signal being based on the quality signal.